Best exhaust for an 87 Grand National?

Dec 27, 2021
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Just bought an 87 GN and looking to improve the sound and performance :)

Considering a Magnaflow system, but open to thoughts/suggestions. Thanks!
 
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motorheadmike

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Nov 18, 2009
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ck80

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Feb 18, 2014
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4"? for a v6?
Really there's no one good answer here.

Much of it depends on how far you are taking modifications, then mix in personal preference.

The best option I could offer is if you don't NEED to make a change right now, head to some club meetings nearby for ttype and gn owners. The guys would be more than happy to talk about what mods they did, then start up a car and give it a Rev or two.

There's no substitution for hearing it for yourself, especially considering how interrelated system choice is to mods planned/performed.
 
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blk7gxn

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Its truly a balance of performance, a quality installation, look of quality, and sound your looking for. GN's (I.M.O.O) came stock with duel exhaust, and should remain this way to get the true unique sound. With that being said, no more than 3" AT MOST. Anyone who puts a 4" exhaust on a GN knows nothing about engineering, performance tuning or takes pride in the quality of their work, because you will have to either modify or hack your car to do the install. CONGRATULATIONS on your purchase and I wish you the best with your decision!

(personally, whatever you do decide to go with, I would look for a quality stainless steel exhaust to ensure a great look for years to come)
 

scoti

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Sep 5, 2019
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Its truly a balance of performance, a quality installation, look of quality, and sound your looking for. GN's (I.M.O.O) came stock with duel exhaust, and should remain this way to get the true unique sound. With that being said, no more than 3" AT MOST. Anyone who puts a 4" exhaust on a GN knows nothing about engineering, performance tuning or takes pride in the quality of their work, because you will have to either modify or hack your car to do the install. CONGRATULATIONS on your purchase and I wish you the best with your decision!

(personally, whatever you do decide to go with, I would look for a quality stainless steel exhaust to ensure a great look for years to come)
That's a pretty presumptuous statement listing 4 negatives if one were to go larger than the 3";

* Knows NOTHING about engineering
* Knows NOTHING about performance tuning
* Knows NOTHING about taking pride in the quality of their work
* Would have to HACK the car to do the install

It's also possible their skill level & modification depth is beyond your ability?

I 100% agree w/you about balancing things for your needs & I wouldn't do a 4" set-up but I have no doubt someone w/decent fab skills could AND could do it right. I also have no doubt someone could have enough performance tuning that the 4" exhaust could compliment their set-up. There are some powerful OE block GN set-ups out there.
 
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CopperNick

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Feb 20, 2018
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Okay, first thing here is, is your ride turboed or not? Second, has anything been done to the engine, cam, etc.? What transmission and what rear end gears? Asking all this because all of this has a bearing on how the car will perform and by extension what kind of pipes might be best for getting your motor to exhale most effectively.

Notice I am Not getting into the what size fits what discussion. My only and personal thought in that direction is that big pipes are there to move lots of exhaust. If the motor isn't pushing heavy cubes or doing some serious breathing, well then..................


One thing you might run into is the concepts of "H" pipe vs "X" pipe down stream from the exhaust manifolds or headers. Again, l i mention it but offer no opinion. For my Monte I run true duals but that is my personal preference and not necessarily the most appropriate for greatest performance.

As for hanging them, lately I've been choosing to use the Vibrant sleeve clamps for any mechanical connections and went wire mig and butt connections when i had to tweak the down range pipes for length or curvature/shape. If you go kit it is probable you will have to trim your selected sections for length or, again, tweak them in one way or another for best fit.

One other thought, the classic shape for exhaust pipes is round. That said there are a couple of mfgr's who have started to offer oblong pipes, meaning the pipe gets put through a special extruder during production to reshape it from round to sort of rectangular with curved corners ala Nascar. Good for ground clearance if that is an issue.



Nick
 
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blk7gxn

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(It's also possible their skill level & modification depth is beyond your ability?) Now who is being presumptuous?

Its simply called science and balance, between engineering and common sense. Most people doing upgrades use 3" cold air intake to a 4" AT MOST. If matching this to a duel 3", this is PLEANTY to handle the CFM and thermal expansion flowing through their air pump ( Engine). Do the math for thermal expansion, when CFM mass is heated it expands in volume but NOT in mass. It would be less dense (hence the smaller exhaust valves and exhaust ports as opposed to the intake valves and ports). This is also why duel 3" is the MAX you would ever need for a Turbo 3.8 V6.

When someone starts hacking their suspension or other areas of their undercarriage to install over killed exhaust systems, it becomes senseless. I compare it to the people who roll smoke with their diesel trucks with a 10" exhaust tip hanging off the back, To each their own, I personally like to see things flow together nicely and use formulas and math, not just wing things, there is a science to everything, especially a SFI Turbo engine. Another down side is clearance issues not only with suspension, but with the ground, for WHAT purpose.
 
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scoti

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Sep 5, 2019
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Texas
(It's also possible their skill level & modification depth is beyond your ability?) Now who is being presumptuous?

Its simply called science and balance, between engineering and common sense. Most people doing upgrades use 3" cold air intake to a 4" AT MOST. If matching this to a duel 3", this is PLEANTY to handle the CFM and thermal expansion flowing through their air pump ( Engine). Do the math for thermal expansion, when CFM mass is heated it expands in volume but NOT in mass. It would be less dense (hence the smaller exhaust valves and exhaust ports as opposed to the intake valves and ports). This is also why duel 3" is the MAX you would ever need for a Turbo 3.8 V6.

When someone starts hacking their suspension or other areas of their undercarriage to install over killed exhaust systems, it becomes senseless. I compare it to the people who roll smoke with their diesel trucks with a 10" exhaust tip hanging off the back, To each their own, I personally like to see things flow together nicely and use formulas and math, not just wing things, there is a science to everything, especially a SFI engine. Another down side is clearance issues not only with suspension, but with the ground, for WHAT purpose.
I stated "it's also possible"... That's not assuming anything about your abilities.
 
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motorheadmike

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Nov 18, 2009
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4"? for a v6?

Yup. Built right with a good muffler it works mint.


Natasha was in her first trimester taking videos on a very hot August day:

 
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